Raman spectroscopy of intact rat and mouse lenses shows the quantitative conversion of sulfhydryl group to disulfide in the nucleus during aging. Continuous irradiation with long wave ultraviolet light in vivo decreases in both -SH and S-S when compared to control lenses. The rate of -SH and S-S conversion is not the same for the lenses of different species. Examination of lenses from rabbit (4 mos. to 4 yrs.), buffalo (3 yrs. to 14 yrs.) and monkey (still-born to 3 yrs.) reveals that the Raman intensity at 2580 per cm 1 does not change appreciably within the ages indicated.